1. Field of the Invention
The present invention relate to a stator of a commutator motor which is configured so that a stator coil can be cooled efficiently.
2. Description of the Related Art
As known well, a stator of a commutator motor shown in FIGS. 5 and 6 is constituted by a stator core 1, and a stator coil 2 wound in a slot of the stator core 1. The stator coil 2 includes coil end portions 2a protruding axially outward from axially opposite end portions of the stator core 1. The stator coil 2 is connected, through four lead wires 3, to an electric source not shown. The stator coil 2 is supplied with electricity through the lead wires 3.
While the motor runs, the stator coil 2 generates heat so that the temperature rises. Therefore, a cooling fan not shown is generally provided to cool the coil end portions 2a by cooling air. Therefore, the sectional shape of a coil bundle 2b in each coil end portion 2a is formed to be a rectangle having a large surface area to increase the cooling surface area to thereby improve the cooling effect.
For example, in order to change the conventional coil bundle 2b having the 1:1 aspect ratio of the circumferential direction (vertical) to the axial direction (horizon) in sectional size into a coil bundle 2b shaped like an axially long rectangle having the same sectional area as that of the conventional coil bundle 2b but having a surface area not smaller than 1.5 times as large as that of the conventional coil bundle 2b, the axial size of the coil bundle 2b must be enlarged to be not smaller than about 2.6 times as large as that of the conventional coil bundle 2b. To enlarge the shape of the coil bundle 2b axially or radially to thereby increase the surface area thereof is to increase the volume of the motor. Because of restriction of size in design in which the miniaturization of products is regarded as importance, there is some limitation in the measures to enlarge the coil bundle 2b to increase the cooling surface area thereof.
An object of the present invention is to eliminate the defects in the prior art and increase the heat-radiating surface area of a coil bundle without increase in the number of parts and without any large change of the shape of the coil bundle to thereby improve the heat-radiating performance of a stator coil.
The foregoing object is achieved by dividing at least one of coil end portions protruding in a bundle from a stator core into at least two portions along a radial direction and by providing a space between the divisions of the coil end portion so that cooling air passes through the space.